1. Field of the Invention
The present invention relates to nitro group-containing naphthoquinone derivatives and to a photosensitive material for electrophotography which contains a nitro group-containing naphthoquinone derivative as an electron transporting agent and is used for the electrophotographic copy, printer and common paper facsimile.
2. Description of the Prior Art
In an electrophotographic method, an electrophotosensitive material is electrically charged and is exposed to image-bearing light to form an electrostatic latent image which is, then, developed into a toner image in a state where a developing bias voltage is applied, and the formed toner image is transferred onto a transfer paper or the like paper and is fixed to form an image. This electrophotographic method is extensively used for the digital or analog copy, printer and common paper facsimile.
A selenium photosensitive material and an amorphous silicon photosensitive material have heretofore been used for the electrophotography. In recent years, however, an organic photosensitive material (OPC) has also been extensively used. Representative examples of the organic photosensitive material include a laminated-layer photosensitive material of the separated function type in which a charge-generating agent (CGM) and a charge-transporting agent (CTM) are laminated one upon the other as separate layers, and a single-layer photosensitive material in which the CGM and the CTM are formed as a single dispersion layer.
As the charge-generating agent, there have been known a variety of inorganic or organic charge-generating agents such as selenium, selenium-tellurium, amorphous silicon, pyrylium salt, azo pigment, disazo pigment, trisazo pigment, anthanthrone pigment, phthalocyanine pigment, indigo pigment, threne pigment, toluidine pigment, pyrazoline pigment, pyranthrone pigment, perylene pigment and quinacridone pigment. As the charge-transporting agent, there have been known positive hole-transporting agents such as poly-N-vinylcarbazole, phenanthrene, N-ethylcarbazole, 2,5-diphenyl-1,3,4-oxadiazole, 2,5-bis-(4-diethylaminophenyl)-1,3,4-oxadiazole, bis-diethylaminophenyl-1,3,6-oxadiazole, 4,4'-bis(diethylamino)-2,2'-dimethyltriphenylmethane, 2,4,5-triaminophenylimidazole, 2,5-bis(4-diethylaminophenyl)-1,3,4-triazole, 1-phenyl-3-(4-diethylaminostyryl)-5-(4-diethylaminophenyl)-2-pyrazoline, p-diethylaminobenzaldehyde-(diphenylhydrazone), tetra(m-methylphenyl) methaphenylenediamine, N,N,N',N'-tetraphenylbenzidine derivative, N,N'-diphenyl-N,N'-dixylylbenzidine, as well as electron-transporting agents such as 2-nitro-9-fluorenone, 2,7-dinitro-9-fluorenone, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2-nitrobenzothiophene, 2,4,8-trinitrothioxanthone, dinitroanthracene, dinitroacridine, dinitroanthraquinone, naphthoquinones, and 3,5-dimethyl-3',5'-di-t-butyldiphenoquinone.
Among the charge-transporting agents, however, very few electron-transporting agents satisfy a practicable level. Even the 3,5-dimethyl-3',5'-di-t-butyldiphenoquinone which has been regarded to exhibit excellent sensitivity, is not still satisfactory in regard to the sensitivity.
Thus, an electron-transporting agent that exhibits an increased degree of sensitivity has been demanded in the field of electrophotography.